Money stock vs. M1 vs M2. As toddster pointed out when you cash in a CD the money therein reverts from M1 to Money stock. So when you sell a stock the funds go into the measures of money supply also as long as you put the proceeds into a money market fund or checking account of some kind.
The illusion is you think a change in *your* holdings of money, are a change in the amount of money there is. Not so.
Money is the debt of a bank. The money supply increases when banks run up the size of their balance sheets, both the liabilities side (their debts, which are money) and their asset side (their loans and other claims on the rest of us).